II/390 EROS light curve data base (EROS coll., 2025)
EROS light curve database.
EROS collaboration, Afonso C., Albert J.-N., Ansari R., Aubourg E.,
Beaulieu J.-P., Blaineau T., Coutures C., Derue F., Glicenstein J.-F.,
Goldman B., Hamadache C., Lasserre T., Le Guillou L., Lesquoy E.,
Magneville C., Mansoux B., Moniez M., Palanque-Delabrouille N.,
Perdereau O., Rich J., Spiro M., Tisserand P.
<Astron. Astrophys., 706, A189 (2026)>
=2025yCat.2390....0E 2025yCat.2390....0E
=2026A&A...706A.189A 2026A&A...706A.189A (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Milky Way ; Stars, variable;
Binaries, eclipsing ; Photometry
Mission_Name: EROS
Keywords: catalogs - surveys - microlensing - Magellanic Clouds - Milky Way -
stars, variable - binaries, eclipsing - photometry
Abstract:
The project called Experience de Recherche d'Objets Sombres (EROS)
carried out photometric surveys of dense stellar fields toward the
Magellanic Clouds (LMC and SMC), the Galactic bulge and Galactic
spiral arms in the period 1990-2003. The main goal of the experiment
was to search for the Galactic dark matter in the form of massive
compact objects (machos) through the gravitational microlensing
effect.
The historical record of the flux variations in the monitored stars by
EROS-2 will be a unique asset for time-domain astronomy and to
complement current and future searches of transient sources.
We describe the set of light curves that was obtained with the EROS-2
program from 1996 to 2003, when more than 86 million stars were
monitored. The set is publicly released through the Centre de Donnees
de Strasbourg (CDS). This dataset includes 28.7 and 4.0 million light
curves in the LMC and SMC, 42.9 million light curves in the Galactic
bulge, and 10.4 million light curves toward the Galactic spiral arms
and has several hundred measurements for each object. The data from
EROS-1 are also being released.
The object catalog, light curves, and images are accessible through
the CDS portal. This is useful for determining the past behavior of
newly discovered variable objects.
Description:
The EROS project (Experience de Recherche d'Objets Sombres) carried
out photometric surveys of dense stellar fields towards the Magellanic
Clouds (LMC and SMC), the Galactic Bulge and Galactic spiral arms,
over the period 1990-2003.
The main goal of the experiment was to search for the Galactic Dark
Matter in the form of massive compact objects (machos), through the
gravitational microlensing effect.
The historical record of the flux variations of the monitored stars by
EROS-2 are a unique asset for time domain astronomy and to complement
current and future searches of transient sources.
The set of light curves obtained by EROS-2 program over the years 1996
to 2003, monitoring more than 86 million stars, is available at the
Centre de Donnees de Strasbourg (CDS).
The numbers of light curves in this data set are 28.7 and 4.0 million
in LMC, respectively SMC, 42.9 million in the Galactic Bulge and 10.4
million towards the Galactic spiral arms, with several hundred
measurements for each object.
Data from the first phase of the project (EROS-1, 1990-95) will also
be available soon.
A description of the released data can be found in Afonso et al,
A&A, 706, A189 (arXiv:2512.12745).
EROS stands for "Experience pour la Recherche d'Objets Sombres". Its
main objective is the search and the study of dark stellar bodies,
so-called "brown dwarfs" or "MACHOs" which belong gravitationally to
our Galaxy. This is made possible by their gravitational microlensing
effects on the light from stars in the Magellanic Clouds (two dwarf
galaxies orbiting our own Milky Way).
EROS I :
EROS started in 1990. In its first phase the collaboration developped
two complementary programs both operated at the La Silla observatory
(ESO). One used a 40cm telescope equipped with a 3.5 million pixel
CCD camera and looked for short timescale microlensing phenomena (one
hour to a few days). No candidate were found, in this timescale range.
On the other hand, 380 photographic plates were obtained using the
1 meter Schmidt ESO telescope, alternately with a blue and a red filter.
These plates have been digitized using the MAMA and then analysed. Two
candidates were found in 1993, that could be interpreted as
microlensing events, out of about 8 million stars surveyed. (since
that time, the second candidate was observed by EROS II to vary again,
in 1999, thus effectively removing it from the list of microlensing
candidates.)
EROS II :
To continue more economically the same program, and get rid of the
difficulties inherent to photographic plates calibration, and increase
its sensivity, the collaboration is currently building a new
apparatus. It is based on a 1.5m telescope recuperated from french
observatories (so called the MARLY telescope). This telescope will be
equiped with a new CCD camera and will be guided using another smaller
CCD camera. Different components are under construction ; first tests
should take place this (1995) spring in the OHP observatory (in
France). Installation in ESO in place of the existsing 40cm telescope
is scheduled this (1995) summer.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
xtinfo.dat 119 1723399 List of individual images
catlist.dat 119 6516 Top level view of the whole data set
(catlist.xcatinfo)
xcat.sam 187 1000 Static sky catalogue (85287091 sources)
xtime.sam 252 1000 Individual light curves (37654139855 rows)
--------------------------------------------------------------------------------
See also:
J/A+AS/109/447 : Eclipsing binaries EROS catalogue (Grison+, 1995)
J/A+A/303/137 : EROS Variables: Cepheids in the bar of LMC (Beaulieu+ 1995)
J/A+A/389/149 : EROS II periodic stars towards Galactic spiral arm
(Derue+, 2002)
J/A+A/454/185 : EROS-2 microlensing parameters (Hamadache+, 2006)
J/A+A/495/249 : EROS-2 beat Cepheids in Magellanic Clouds (Marquette+, 2009)
J/A+A/500/1027 : EROS CMD towards 4 Galactic spiral arms fields (Rahal+, 2009)
Byte-by-byte Description of file: xtinfo.dat
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Bytes Format Units Label Explanations
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1- 22 A22 --- FileName Name of CCD image
24- 34 F11.5 d MJD Modified Julian Day
36- 45 F10.5 d HJD EROS Heliocentric Julian Day (HJD-2449999.5)
47- 54 F8.2 --- Bgd ? Image background (in ADU units)
56- 61 F6.3 pix PSF-X ? PSF width along X
63- 68 F6.3 pix PSF-Y ? PSF width along Y
70- 75 F6.3 --- PSF-rho ? PSF mean ellipticity
77- 88 F12.3 --- Abs ? Absorption in the EROS filter
90- 97 F8.5 --- AirMass ? Airmass (sec z)
99-119 A21 --- Date Observing date(s) (UTC-TBC) (YYYY-MM-DD)
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Byte-by-byte Description of file: catlist.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Field Field identification, followed by the CCD
number (0-7) and quarter (k,l,m,n)
(ccd-quarter) (1)
9- 13 I5 --- Nstars Number of stars in the corresponding object
catalog (xcat file) (nstars)
15- 23 F9.5 deg RAmin Limit in right-ascension covered by the
corresponding object catalog (ramin)
25- 33 F9.5 deg RAmax Limit in right-ascension covered by the
corresponding object catalog (ramax)
35- 43 F9.5 deg DEmin Limit in declination covered by the
corresponding obect catalog (decmin)
45- 53 F9.5 deg DEmax Limit in declination covered by the
corresponding obect catalog (decmax)
55- 59 I5 --- NR10 Number of stars with better than 10 percent
photometric precision in Reros band (nr10)
61- 65 I5 --- NB10 Number of stars with better than 10 percent
photometric precision in Beros band (nb10)
67- 71 F5.2 mag Rlim19 Upper magnitude limits for stars with
photometric precision better 10 percent
in Reros (mr10)
73- 77 F5.2 mag Blim19 Upper magnitude limits for stars with
photometric precision better 10 percent
in Beros (mb10)
79- 83 F5.2 mag Rlim90 Upper magnitudes limits encompassing
90 percent of stars in Reros (mrlim)
85- 89 F5.2 mag Blim90 Upper magnitudes limits encompassing
90 percent of stars in Beros (mblim)
91- 96 F6.3 arcsec oRA Mean offset of original EROS-2 astrometry
compared to Gaia astrometry (Gaia
Collaboration, 2023A&A...674A...1G 2023A&A...674A...1G)
in right-ascension (raeros-ragaia)
98-103 F6.3 arcsec oDE Mean offset of original EROS-2 astrometry
compared to Gaia astrometry (Gaia
Collaboration, 2023A&A...674A...1G 2023A&A...674A...1G) in
declination (deceros-decgaia)
105-108 I4 --- NExp Number of exposures or measurements for the
corresponding xcat file (nexp)
110-119 A10 "date" Date The observation date of the first image
used to create the red band reference image
(epoch) (2)
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Note (1): For example sm0023m refers to the SMC field 002, CCD 3 and quarter m.
Note (2): This defines the epoch of the celestial source positions on the image
plane that have been used to determine the astrometric projection .
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Byte-by-byte Description of file: xcat.sam
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Bytes Format Units Label Explanations
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1- 12 A12 --- EROS Unique Identifier
14- 23 F10.6 deg RAdeg Right ascension on reference image, J2000 (Ra)
25- 34 F10.6 deg DEdeg Declination on reference image, J2000 (Dec)
36- 41 F6.3 mag Rmag Magnitude on reference image in the EROS R band
(MagR)
43- 51 F9.3 mag eRmag/Rmed rms uncertainty of magnitude in the EROS R band
wrt. Rmed (sigpullr)
53- 59 F7.2 pix XR Pixel coordinate in the EROS R band along X axis
61- 67 F7.2 pix YR Pixel coordinate in the EROS R band along Y axis
69- 74 F6.3 mag Bmag Mean magnitude on reference image in the EROS B
band (MagB)
76- 84 F9.3 mag e_Bmag Mean magnitude uncertainty on reference image
in the EROS B band (ErrMB)
86- 92 F7.2 pix XB Pixel coordinate in the EROS B band along X axis
94-100 F7.2 pix YB Pixel coordinate in the EROS B band along Y axis
102-111 F10.2 --- FluxR Flux in the EROS R band (in adu units) (fluxr)
113-128 F16.2 --- FluxB Flux in the EROS B band (in adu units) (fluxb)
130-133 I4 --- Nlc Number of epochs in light curve (nlc)
135-140 F6.3 mag RmagMed Median magnitude in the EROS R band (medianr)
142-149 F8.3 mag e_RmagMed ? rms uncertainty of magnitude in the EROS R
band wrt. RmagMed (sigpullr)
151-156 F6.3 mag BmagMed Median magnitude in the EROS B band (medianb)
158-165 F8.3 mag e_BmagMed ? rms uncertainty of magnitude in the EROS B
band wrt. BmagMed (sigpullb)
167-176 F10.6 deg RAGdeg Right ascension (ICRS)
178-187 F10.6 deg DEGdeg Declination (ICRS)
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Byte-by-byte Description of file: xtime.sam
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- EROS Unique Identifier (erosid)
14- 23 F10.6 deg RAdeg Right ascension on reference image, J2000 (ra)
25- 34 F10.6 deg DEdeg Declination on reference image, J2000 (dec)
36- 45 F10.5 d HJD EROS heliocentric julian date (date)
47- 52 F6.3 mag Rmag ? Magnitude in the EROS R band (MagR)
54- 82 F29.3 mag e_Rmag ? Magnitude uncertainty in the EROS R band
(ErMagR)
84- 89 F6.3 mag Bmag ? Magnitude in the EROS B band (MagB)
91-123 F33.3 mag e_Bmag ? Magnitude uncertainty in the EROS B band
(ErMagB)
125-135 F11.2 --- FluxR ? Flux in the EROS R band (in adu units)
(fluxr)
137-165 F29.2 --- e_FluxR ? Flux uncertainty in the EROS R band
(in adu units) (efluxr)
167-177 F11.2 --- FluxB ? Flux in the EROS B band (in adu units)
(fluxb)
179-211 F33.2 --- e_FluxB ? Flux uncertainty in the EROS B band
(in adu units) (efluxb)
213-227 F15.3 --- chi2R ? chi-square of PSF fit to the EROS R image
(chi2r)
229-244 F16.3 --- chi2B ? chi-square of PSF fit to the EROS B image
(chi2b)
246-252 A7 --- DateCode EROS filename-format date (datecode)
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Acknowledgements:
From Bertrand Goldman, bertrand.goldman(at)isunet.edu
This catalogue is dedicated to the memory of our EROS collaborators
Johannes Andersen, Pierre Bareyre, Florian Bauer, Sergio Char,
Jean Guibert, Eric Maurice, Alain Milsztajn, Luciano Moscoso, and
Cecile Renault.
(End) Patricia Vannier [CDS] 16-Sep-2025